1. Field of the Invention
The present invention relates to a honeycomb regenerator for recovering a waste heat in an exhaust gas by passing the exhaust gas and a gas to be heated alternately therethrough, which is constructed by stacking a plurality of honeycomb structural bodies and especially relates to the honeycomb regenerator used in an exhaust gas having a high temperature or a corrosive exhaust gas having a high temperature.
2. Description of Related Art
In a combustion heating furnace used for industries such as a blast furnace, an aluminum melting furnace, a glass melting furnace or the like, a regenerator used for improving a heat efficiency, in which a firing air is pre-heated by utilizing a waste heat of an exhaust gas, has been known. As such regenerators, Japanese Patent Laid-Open Publication No. 58-26036 (JP-A-58-26036) discloses regenerators utilizing inexpensive ceramic balls, saddles, pellets or the like. Such regenerators mentioned above can be constructed in an inexpensive manner. However, there are such drawbacks, that a pressure loss is higher when the exhaust gas or an air for firing (i.e. the gas to be heated) is passed through the regenerators, and, that a heat exhanging area of the regenerators per a unit volume is smaller.
In order to overcome such drawbacks, Japanese Patent Laid-Open Publication No. 4-251190 (JP-A-4-251190) discloses a regenerator utilizing honeycomb structural bodies. In the honeycomb structural bodies, a pressure loss is lower when the exhaust gas or the like is passsed therethrough, and a heat exchanging area of the regenerators per a unit volume is larger. Therefore, it is possible to perform a heat exchanging operation effectively.
Generally, the exhaust gas sometimes includes low temperature solidifying components such as organic polymer or the like. In the combustion heating furnace used for industries, a processing apparatus or the like, in which the regenerators mentioned above are utilized, the regenerators positioned at an inlet portion of the gas to be heated are characterized by relatively low temperature. In this case, the low temperature solidifying components in the exhaust gas are sometimes solidified on the regenerators having a low temperature, a pressure loss becomes higher when the exhaust gas or the air for firing is passed through the regenerators. Therefore, for example, when use is made of the known inexpensive regenerators, the regenerators are changed in a short time period and used again after they are washed. On the other hand, even when use is made of the honeycomb structural body, the low temperature solidified components in the exhaust gas is solodified in through holes defining cells of the honeycomb structural body and the through holes are stuffed. Therefore, there is a drawback such that a pressure loss becomes also higher when the exhaust gas or the like is passed through the honeycomb structural body.
In order to overcome the drawback mentioned above, a high temperature gas is introduced from an inlet side of the air for firing by utilizing, for example, a burner so as to remove the low temperature solidifying components stuffed in the through holes by firing or vaporizing them. This means is hereinafter abbreviated as after burner. The after burner is utilized since the honeycomb structural body is very expensive as compared with the known regenerators and since the honeycomb structural body is liable to be fractured and a simple regenerating means such as changing or re-using after washing is not applied to the honeycomb structural body.
However, if the low temperature solidifying components are to be removed by the after burner as mentioned above in the honeycomb structural body, it is necessary to perform such removing operation in a relatively short time period during a furnace operation stop. Therefore, there occurs a problem that the honeycomb structural body is often fractured due to a thermal shock or the like. Moreover, since the honeycomb regenerator according to the invention is constructed by stacking a plurality of honeycomb structural bodies, there occurs a problem that the stacked honeycomb is broken and is not served as the honeycomb regenerator if the lower honeycomb structural body faced to the gas to be heated is fractured.